Process for the production of electrodes for electro-chemical purposes



May 27, 1958 H. VOGT 2,836,641 PROCESS FOR THE PRODUCTION OF ELECTRODESFOR ELECTED-CHEMICAL PURPOSES Origmal F1166. Apnl 25, 1949 -bonate mayserve as spacer bodies.

scribed suspension in a thin layer upon the carrier foil,

United States PROCESS FOR PRSDUCTION F ELEC- gno gus FORELECTRO-CHEMICAL PUR- Hans Vogt, Erlau, Germany Original applicationApril 25, 1949, Serial No. 89,416,

now Patent No. 2,681,375, dated June 15, 1954. Divizdseg and thisapplication April 26, 1954, Serial No. 4 24 Claims priority, applicationSweden May 4, 1948 6, Claims. 01. 136-20) The present invention relatesto electrodes for electric batteries.

It is an objectof the present invention to provide a simple andinexpensive process for producing electrodes which combine highefficiency and low resistance with low weight.

Another object of the invention is to provide asimple and inexpensiveprocess for producing electrodes, of the Fig. 1'.

Fig. 3 is afragmentary cross section through another electrode producedin accordance with the invention, likewise shown with exaggeratedthickness forreasons of claiity.

Figs. 4 and S are diagrams illustrating the manner in which. suchelectrodes are produced in accordance with .the invention.

According to the invention, metal powders are deposited upon,andsintered onto, a thincarrier sheet to form mioro-porousmeta-l layersthereon. The carrier sheet may be formed by a solid or a perforatedmetal ,foil fine wire gauze, feltedmetal filaments or'the like,

of a suitable thickness ranging for instance from 0.2 mm.

to .05 mm, and the micro-porousmetal powder layer should ..be. of-,suchthicknessethat the completed electrode has the appearance of a thinfoilthat may be less than 1 mm; in thickness, and preferably in therange of from .2-and .8 mrruyMetal powders of low Weight'per unitvolume, i. 6-, less-than 1.5 grams per cmfi, should preferably beemployed, such as nickel powder or iron powder. These powders'may beproduced by chemical or thermal decomposition of salts of the respectivemetals (for instance, nickel nitrate or iron nitrates) at temperatomsfrom 400 C. to 500 C. and subsequent reduction at temperatures from 600C. to 800 C.

According. to a preferred form of the invention L prepared -a liquidsuspension from a light metal powder,-

pore-formation promoting spacer bodies, and a. suitable liquid, such aswater or a'hydro-carbon. Carbon or carbonate particles'respecially.particles of ammonium car- I deposit the de dry it on the carrier foiland sinter -it in a reducingyatmosphere at temperatures between 600 C.and 1,000" C. to solidify itinto a micro-porous metal layer that adheresto: the carrier .foil. Thepore-formation prOmoting materials may beremoved before, during or after the actual sintering process.

' atent iron or cobalt.

2,83%,hdl

, Patented May 27,

While the metal powder maybe spread over, or sprayed onto, the carrierfoil I prefer its application by a clipping process. For'this purposethe carrier foil may be passed in a continuous process through a metalpowder suspension and, depending upon the consistency of the suspension, this process may be repeated to obtain a desired thickness. Thesubsequent drying, sintering and impregnation of the coated carrier withthe electrochemically active substances may then likewise occur in acontinuous process. in this manner I produce a ductile electrodeskeleton which is very suitable for the reception of the properhydroxides, such as hydroxides of cadmium, nickel, This skeleton may beimpregnated in the customary manner by introducing salts of any one ofthesemetals into its pores and reacting these salts' with an alkali toprecipitate the electrochemically active hydroxides which then adherefirmly to the pores. In the finished electrode the Weight of the dryhydroxides incorporated therein may be equal to the Weight of theelectrode skeletion.

According to a modified form of my process, two paper strips areimpregnated with mineral substances, are then coated on one side withthe metal powder emulsion in a continuous process, and are subjected toa preliminary drying process, whereupon they are pressed with theircoated faces against an interposed carrier sheet in the form of anextremely thin texture of light metal. 'Ihereafter the drying process iscompleted, and the joinedstrips are sintered, which may be performed ina continuous process or may be carried out after the strips have beencut into lengths of appropriate size and are stacked in packs or piles.v

Referring now to the drawings, the electrodes illustrated in Figs 1 and3 comprise a metal foil 1 which may be a sheet of nickel or .iron havinga thickness of from .about .03 to .05 mm. Said foil may be solid, asshown" in Fig. l, or perforated, as shown in Fig. 3. Sintered uponitssides are micro-porous metal layers 2 whose interstices are filled withthe active hydroxides. In Fig. 3 the perforations in the foil areindicated at' 3, and the reference numeral 4 designates relatively largecavities within the metal layers 2 which are produced by the previouslymentioned spacer bodies that are removed from the layer prior, during orafter the sintered process. Such cavities improve the ratio of hydroxidevolume to metal weight to asubstantialdegree. p Fig. 4 illustratesdigrammatically one of the methods for producing electrodes of the typeillustrated in Figs. 1,

'2 and 3; According to Figure 4a carrierstrip 30 supplied from a feedroller (not shown) passes underneath a roller 35 through a vessel 31containing a suspension of suitable consistency that comprises a metalpowder, poreformation promoting spacer bodies, and adhesive and adisposed within a vertical furnace 37, to dry the coating and drive offthe spacer bodies. Thereafter the strip passes through a second furnace(not shown) within which the metal powder layers are sintered in areducing -atmosphere at temperatures ranging from 600 C. to 1,000 .C.Thereafter the strip passes through a water cooled jacket 38 'from whichit emerges between rollers 39 anddl) to pass onto a reel 41 or similardevice. It may also successively pass through installations (not shown)wherein any residual spacer bodiesin the metal layers aredissolved andwherein the electrode may, in consecutive stages, be =impregnatedwithmetal salts, dried, treated to precipitate the hydroxides, washedand subjected to a final drying operation.

According to the method illustrated in Fig. 5, two strips 49 of glazedpaper pass from supply reels 50 underneath the uppermost rollers of twobatteries of superposed rollers 51. The lowermost rollers of saidbatteries are ribbed and are immersed in an iron powder suspension. Inthis manner the lower faces of the paper strips 49 are coated with alayer of the iron powder suspension. Both strips then travel pastheating elements 52 by which the applied layers are appropriately dried.Thereupon the strips pass between two rollers 53 which press them withtheir coated faces against a metal netting 54 that is fed from a supplyreel 55 into the space between the rollers 53. The composite stripemerging from between the rollers 53 may then be treated in the samemanner as described in connection with Fig. 4. Alternatively, thecomposite strip may be guided along a horizontal path and automaticallycut into pieces of suitable length that are stacked into packs. Theseare then sintered within a furnace in a reducing atmosphere at asuitable temperature, such as 800 C., for a period of from one to twohours. During the sintering process the paper strips are burnt oif, butthe mineral glazing substances contained in said paper strips preventthe superposed metal powder layers from sintering together. Hence, theindividual electrodes retain their identity and may, after a superficialcleaning, be impregnated with the electrically active sub stances in theusual manner.

The resistance of batteries comprised of electrodes produced inaccordance with the present invention is extremely low, i. e., aboutone-tenth to one-twentieth of batteries comprised of conventional sheetmetal electrodes or conventional sinter electrodes. Batteries made fromelectrodes produced in accordance with the invention are, therefore,able to stand far stronger charging and discharging currents thanpreviously permissible and their efiiciency is improved accordingly.Furthermore, the thin electrodes produced in accordance with theinvention may easily and quickly be impregnated and their cavities maybe filled to capacity with the electro-chemically active hydroxides,whereas the impregnation of the thick sinter electrodes of conventionaldesign presented erious difiiculties.

While I have illustrated my invention with the aid of an exemplaryprocess, it will be understood that I do not wish to be limited to thespecific steps and temperatures given by way of example, which may bedeparted from before departing from the scope and spirit of theinvention.

This is a division of my co-pending patent application Serial No.89,416, filed April 25, 1949, now U. s Patent No. 2,681,375, dated June15, 1954, and claiming the priority of Swedish patent application No.3,902, filed May 4, 1948.

I claim:

1. The process of producing electrodes for electrochemical purposes in acontinuous operation which comprises depositing iron group metal powderin a continuous process onto both faces of an iron group metalliccarrier strip to form a thin coating on each face thereof, passing thestrip thus coated through a sintering zone maintained at a sinteringtemperature for the metal deposited on the carrier simultaneously totransform each metal powder coating into a micro-porous metal layer andsinter it onto said carrier strip, subsequently impregnating the layerbearing strip with electrochemically active hydroxides and cutting thestrip into portions of appropriate length.

2. The process of producing electrodes for electrochemical purposes in acontinuous operation which comprises applying a liquid suspension of aniron group metal powder containing pore-formation promoting materials ina continuous process to an iron group metallic carrier strip to form athin coating on each face thereof simultaneously, passing the strip thuscoated through a heating zone maintained at a sintering temperature forthe metal 4 powder to drive off said pore-formation promoting materials,transform the metal powder coating into a microporous metal layer, andsinter it onto said carrier strip, subsequently impregnating the layerbearing strip with electrochemically active hydroxides and cutting thestrip into portions of appropriate length.

3. The process of producing electrodes for electrochemical purposes in acontinuous operation which comprises applying a liquid suspension of aniron group metal powder in. a continuous process to an iron groupmetaliic carrier strip of a thickness ranging between 0.2 mm. and .05mm. to form a thin coating on each face thereof simultaneously, passingthe strip thus coated through a sintering zone maintained at atemperature of between 600 C. and 1,000 C. to transform the metal powdercoating into a micro-porous metal layer and sinter it onto said carrierstrip, subsequently impregnating the layer bearing strip withelectrochemically active hydroxides and cutting the strip into portionsof appropriate length.

4. The process of producing electrodes for electrochemical purposes in acontinuous operation which corn prises passing a thin iron group carrierstrip of a thickness ranging from .02 to .05 mm. in continuous processthrough a homogeneous, agitated, liquid suspension of iron group metalpowder containing pore-formation promoting bodies having carbon content,to form thin coatings of said suspension on both faces thereof, dryingsaid coatings and passing the coated strip through a sintering zonemaintained at a temperature between 600 C. and 1,000 C. to drive offsaid pore-formation promoting bodies, transform said coatings intomicro-porous metal layers and sinter them onto said strip andsubsequently impregnating the layer bearing strip with electrochemicallyactive hydroxides.

5. The process of producing an electrode for electrochemical purposes ina continuous operation which comprises applying a thin coat of a liquidsuspension of iron group metal powder in a continuous operation onto twostrips of glazed paper, pressing the coated paper strips with theircoated sides against each other while introducing a thin iron groupmetallic carrier sheet between them, and conducting the composite stripbody through a heating zone maintained at a sintering temperature forthe iron group metal powder applied to the paper strips so as to burnoff the paper strips and transform the metal powder suspension coatsinto micro-porous metal layers, and sinter said layers onto the oppositesides of said metallic carrier sheet. 1

6. The process of producing an electrode for electrochemical purposes ina continuous operation which comprises applying a thin coat of a liquidsuspension of iron group metal powder containing pore-formationpromoting materials in a continuous operation onto two strips of glazedpaper, pressing the coated paper strips with their coated sides againsteach other while introducing a thin iron group metallic carrier sheetbetween them, and conducting the composite strip body through a heatingzone maintained at a sintering temperature for the iron group metalpowder applied to the paper strips so as to burn off the paper strips,drive off the pore-formation promoting materials, transform the metalpowder suspension coats into micro-porous metal layers, and sinter saidlayers onto the opposite sides of said metallic carrier sheet.

References Cited in the file of this patent UNITED STATES PATENTS Re.22,373 Benner et al. Sept. 14, 1943 2,122,053 Burkhardt June 28, 19382,187,086 Koehring Jan. 16, 1940 2,357,536 Morse Sept. 5, 1944 2,368,458Engle Jan. 30, 1945 2,390,160 Marvin Dec. 4, 1945

1. THE PROCESS OF PRODUCING ELECTRODES FOR ELECTROCHEMICAL PURPOSES IN ACONTINUOUS OPERATION WHICH COMPRISES DEPOSITING IRON GROUP METAL POWDERIN A CONTINUOUS PROCESS ONTO BOTH FACES OF AN IRON GROUP METALLICCARRIER STRIP TO FORM A THIN COATING ON EACH FACE THEREOF, PASSING THESTRIP THUS COATED THROUGH A SINTERING ZONE MAINTAINED AT A SINTERINGTEMPERATURE FOR THE METAL DEPOSITED ON THE CARRIER SIMULTANEOUSLY TOTRANSFORM EACH METAL POWDER COATING INTO A MICRO-POROUS METAL LAYER ANDSINTER IT ONTO SAID CARRIER STRIP, SUBSEQUENTLY IMPREGNATING THE LAYERBEARING STRIP WITH ELECTROCHEMICALLY ACTIVE HYDROXIDES AND CUTTING THESTRIP INTO PORTIONS OF APPROPRIATE LENGTH.